1. Field of the Invention
This invention relates in general to offshore well riser adapters and, in particular, to a system for connecting riser adapters to subsea equipment with subsea functionality.
2. Brief Description of Related Art
In offshore drilling operations, the operator will perform drilling operations through a drilling riser. The drilling riser extends between the subsea wellhead assembly at the seafloor and the drilling vessel. The drilling riser is made up of a number of individual joints or sections. These sections are secured to each other and run from a riser deploying floor of the drilling vessel. The drilling riser also normally has a number of auxiliary conduits that extend around the main central pipe. The auxiliary conduits supply hydraulic fluid pressure to the subsea blowout preventer and lower marine riser package.
The lower end of the drilling riser has an adapter that couples to a lower marine riser package (LMRP) for connecting the riser to the LMRP. Various adapters have been employed. The adapter connections include bolted flanges and locking segments radially moveable by screws. The LMRP attaches to a blowout preventer assembly (BOP). The BOP couples by a hydraulic connector to a subsea wellhead assembly at the sea floor. The LMRP also includes an emergency disconnect to quickly release from the BOP. The various hydraulically driven components of the LMRP are supplied with hydraulic fluid and controlled by lines leading to the surface vessel.
In both types of riser adapters, workers use wrenches to make up the bolts or screws. Making up the individual bolts is time consuming. Often when moving the drilling rig from one location to another, the riser has to be pulled and stored. In very deep water, pulling and rerunning the riser is very expensive. At least one automated system is shown in U.S. Pat. No. 6,330,918 for making up riser locking segment screws.
In addition, the automated and non-automated riser adapters fail to provide a way to break out the connection between the riser and the LMRP once the adapter and assembly are on the sea floor. Thus, where emergency events necessitate the ability to quickly disconnect an existing riser from the riser adapter while the LMRP remains on the sea floor, operators cannot quickly do so. This can potentially further exacerbate an already potentially dangerous situation. The emergency disconnect is controlled from the vessel, and the control line could be lost.